Process for preparing phenyl sulfone carboxylic acids

ABSTRACT

A process for preparing phenyl sulfone carboxylic acids which involves contacting an alkyl phenyl sulfone with molecular oxygen while the same is dissolved in a lower carboxylic acid containing cobalt and a methylenic ketone.

I United States Patent [151 3,676,488 Onopchenko et al. [451 July 11, 1972 [54] PROCESS FOR PREPARING PHENYL References fli SULFONE CARBOXYLIC ACIDS UNITED STATES PATENTS [72] Inventors: Anatoll Onoochenko, Monroeville; Johann 2,673,218 3/1954 Caldwell ..260/524 G. D. Schulz, Pittsburgh; Roger C. Wll- 2,245,528 6/1941 Loder ..260/524 liamson, Allison Park, all of Pa. [73] Assignee: Gulf Research & Development Company, p'imary Examiner mnain Weinberg" Pittsburgh p Assistant Examiner-R. S. Weissberg AtrorneyMeyer Neishloss, Deane E. Keith and Joseph J. [22] Filed: May 1, 1970 Carducci [21] Appl. No.: 33,946

[57] ABSTRACT [52] US. Cl. ..260/524 R A process for preparing phenyl sulfone carboxylic acids which [51 Int. Cl. ...C07c 63/02, C07c 147/06 involves contacting an alkyl phenyl sulfone with molecular ox- [58] Field of Search ..260/524R y whil the same is dissolved in a lower carboxylic acid containing cobalt and a methylenic ketone.

10 Claims, No

PROCESS FOR PREPARING PHENYL SULFONE CARBOXYLIC ACIDS This invention relates to a process for preparing phenyl sulfone carboxylic acids.

The preparation of phenyl sulfone carboxylic acids from an alkyl phenyl sulfone using oxidation techniques is considered to be exceedingly difficult as evidenced by Caldwell in U.S. Pat. No. 2,673,218, dated Mar. 23, 1954, and Bennett et al. in U.S. Pat. No. 3,022,320 dated Feb. 20, 1962. When oxidation of p-tolyl sulfone was attempted at various temperature levels in the absence of activators in the Caldwell patent, the methyl groups remained unaffected. Caldwell stated that such oxidation would go only in the presence of a lower aliphatic unsubstituted aldehyde, and that its presence was necessary throughout the reaction period. Caldwell also stated that methylenic ketones would not be effective as activators in the oxidation of an alkyl phenyl sulfone. Bennett et al. attempted the oxidation by using nitric acid as a chemical oxidant.

We have found, contrary to the above, that a methylenic ketone cannot only be used as an activator in the defined reaction, but that in this case yields of desired product acid are exceedingly high and that the same are attained in less reaction time.

The alkyl phenyl sulfone that is oxidized herein can be represented by the following formula:

wherein R, and R are selected from alkyl substituents having from one to 10 carbon atoms, preferably methyl, n, is an integer from to 5, preferably 1, and n is an integer from 1 to 5, preferably 1. Specific examples of alkyl phenyl sulfones that can be used include p-tolyl sulfone, O-tolyl sulfone, m-tolyl sulfone, 3,4-dimethylphenyl sulfone, 2,4-dimethylphenyl sulfone, 3-amylphenyl-3,4-dimethylphenyl sulfone, 2,3 ,4-trioctylphenyl, phenyl sulfone, p-decylphenyl sulfone, 2,3,4,5,6- pentarnethylphenyl-2-butylphenyl sulfone, etc. Of these, we prefer to employ p-tolyl sulfone.

In order to convert the alkyl phenyl sulfone defined above to a phenyl sulfone carboxylic acid, it is necessary to bring the same into contact with molecular oxygen sufficient in an amount at least stoichiometrically to convert at least one of the alkyl substituents on the alkyl phenyl sulfone to a carboxylic acid group. Preferably the amount of molecular oxygen employed, on a molar basis, will be from about one to 100 times the amount stoichiometrically required to convert an alkyl substituent to a carboxylic acid group. The contact with molecular oxygen is effected while the alkyl phenyl sulfone is dissolved in a lower carboxylic acid solvent having from two to six carbon atoms, preferably from two to four carbon atoms. Specific examples of such carboxylic acids are acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, etc. Of these, we prefer to employ acetic acid. The amount of carboxylic acid used can vary over a wide range, but on a weight basis, relative to acetic acid, can be from about 2:1 to about 50:1, preferably from about :1 to about :1.

Also present in the reaction mixture is cobalt, which can be in any form, but is preferably used as a salt soluble in the reaction mixture. Thus, the cobalt compound can be in the form of an inorganic compound or as an organic compound, for example, as a cobaltous or cobaltic chloride, sulfate, nitrate, acetate, propionate, butyrate, isovalerate, benzoate, toluate, naphthenate, salicylate, acetyl acetonate, etc. The amount of cobalt compound employed, as cobalt, relative to acetic acid, on a weight basis, can be from about 0.1 percent to about 10 percent, preferably from about 0.5 percent to about 5 percent.

Additionally required herein as activator is a methylenic ketone, such as methyl ethyl ketone, cyclohexanone, cyclopentanone, cycloheptanone, cyclooctanone, acetylacetone, methyl propyl ketone, diethyl ketone, ltetralone, 2-tetralone, l-decalone, 2-decalone, etc. Of these, we prefer to employ methyl ethyl ketone. The concentration of methylenic ketone in the reaction mixture can be from about 0.5 to about 50 percent, preferably from about one to about 10 percent.

The reaction conditions employed herein are mild. Thus, the temperature can be in the range of about 50 to about 200 C., preferably about to about 125 C., and the pressure desirably in the range of about atmospheric to about 5,000 pounds per square inch gauge, preferably about to about 500 pounds per square inch gauge. The residence time depends on the amount of oxidation desired, but generally can be in the range of about one minute to about 60 hours, preferably about one hour to about 10 hours.

Recovery of phenyl sulfone carboxylic acids can be effected in a convenient manner, since the same are insoluble in the reaction product. Thus, the reaction product can be filtered and the solids washed with water to remove catalyst and lower carboxylic acid therefrom.

The process defined and claimed herein can further be illustrated by the following:

EXAMPLE I That the desired reaction will not proceed in the absence of a methylenic ketone can be seen from the present run. Into an autoclave there was placed 420 grams of glacial acetic acid, 25.2 grams of cobaltous acetate tetrahydrate and 42.3 grams of p-tolyl sulfone. The autoclave was then brought to a temperature of C. and an oxygen pressure of 335 pounds per square inch gauge and maintained under these conditions for a period of 28 hours. At the end of this time the autoclave was cooled, depressured and its contents drained. Filtration of the crude material resulted in 39.0 grams of a white solid which was washed several times with water and dried in a vacuum oven. The filtrate was pink in color, indicating the presence of cobaltous ions. The product failed to dissolve in aqueous sodium hydroxide, and did not indicate the presence of acids by infrared or gas chromatography. Only one sharp peak was obtained on the chromatogram for the p-tolyl sulfone feed. Thus, no reaction occurred.

The above should be contrasted with the results obtained below.

EXAMPLE II A mixture consisting of 420 grams of glacial acetic acid, 25 grams of cobaltous acetate tetrahydrate, 69 grams of methyl ethyl ketone and 50 grams of p-tolyl sulfone was charged to a one-liter autoclave which was pressured with oxygen to about pounds per square inch gauge and heated to a temperature of 105 C. Additional oxygen was then added to raise the pressure in the autoclave to 300 pounds per square inch gauge. The contents of the autoclave were maintained at these conditions for 3 hours, after which the autoclave was cooled, depressured and the contents removed therefrom. The crude reaction product was filtered to remove a solid product, which was washed with water several times to remove traces of catalyst and acetic acid therefrom and then dried in an oven at C. for 5 hours. A total of 56 grams of the desired di-acid, p-phenyl sulfone dicarboxylic acid, of greater than 95 percent purity was recovered, representing a molar yield of 90 percent. The product, which was characterized by infrared and nuclear magnetic resonance spectroscopy, had a melting point of greater than 350 C. and a neutral equivalent of 158.

EXAMPLE III This run was similar to EXAMPLE ll except that the charge consisted of 450 grams of the filtrate from EXAMPLE II, 70 grams of methyl ethyl ketone and 50 grams of p-tolyl sulfone. The contents of the autoclave were held at an oxygen pressure of 300 pounds per square inch gauge and 105 C. for 2.5 hours. The yield of p-phenyl sulfone dicarboxylic acid was 96 percent. This procedure can be repeated many times using the filtrate from a previous run. In the event that water builds up to an excessive level, it can be removed from the filtrate prior to a subsequent oxidation.

The following four runs were carried out using varying amounts of methyl ethyl ketone as activator.

EXAMPLE IV EXAMPLE V Repeating the run of EXAMPLE IV but with grams of methyl ethyl ketone resulted in a yield of p-phenyl sulfone dicarboxylic acid of 89 percent.

EXAMPLE VI When the run of EXAMPLE V was repeated with 8 grams of methyl ethyl ketone and 51.8 grams of p-tolyl sulfone using a residence time of 5.5 hours, the yield of p-phenyl sulfone dicarboxylic acid was 90 percent.

EXAMPLE VIl Repeating the run of EXAMPLE V1 with but only 4 grams of methyl ethyl ketone and 42.9 grams of p-tolyl sulfone using a residence time of 2.5 hours still resulted in a yield of p-phenyl sulfone dicarboxylic acid of 29 percent.

EXAMPLE VIII In this run another methylenic ketone, cyclohexanone, was used. This run was carried out in the same manner as EXAM- PLE l with 380 grams of glacial acetic acid, 29 grams of cyclohexanone, 25 grams of cobaltous acetate tetrahydrate and 30 grams of p-tolyl sulfone. The temperature was 105 C., the oxygen pressure 300 pounds per square inch gauge and the residence time 1.5 hours. The yield of p-phenyl sulfone dicarboxylic acid was 28 percent.

EXAMPLE [X A mixture consisting of 400 grams of glacial acetic acid, 20 grams of cobaltous acetate tetrahydrate. 60 grams of methyl ethyl ketone and 50 grams of 3,4-dimethylphenyl sulfone was charged into a l-liter autoclave and brought to a temperature of C. and oxygen pressure of 300 pounds per square inch gauge. The contents of the autoclave were maintained at these conditions for 4 hours, after which the autoclave was cooled, depressured and the contents removed therefrom. The solvent were evaporated until a dry residue was left in the flask. The organic product was separated from the catalyst by extraction with acetone and the latter evaporated to give 45 grams of white solid which was washed with water, dilute hydrochloric acid, water again, and dried. Treatment of the catalyst with concentrated hydrochloric acid gave an additional 5.7 grams of product. The combined product was analyzed by gas chromatography and was found to consist of 9 percent yield of mono-acid, 64 percent yield of di-acid, and 15 percent yield of a tri-acid mixture. t I

Obviously, many modifications and variations of the invention, as hereinabove set forth, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for preparing phenyl sulfone carboxylic acids which comprises contacting an alkyl phenyl sulfone with molecular oxygen while the same is dissolved in a lower carboxylic acid containing cobalt and a methylenic ketone.

2. The process of claim 1 wherein said alkyl phenyl sulfone contains an alkyl substituent on each ring.

3. The process of claim 1 wherein said alkyl phenyl sulfone contains a methyl substituent on each ring.

4. The process of claim 1 wherein said alkyl phenyl sulfone is p-tolyl sulfone.

5. The process of claim 1 wherein said methylenic ketone is methyl ethyl ketone.

6. The process of claim 1 wherein said methylenic ketone is cyclohexanone.

7. The process of claim 1 wherein the reaction temperature is in the range of about 50 to about 200 C.

8. The process of claim 1 wherein the reaction temperature is in the range of about 80 to about C.

9. The process of claim 1 wherein said lower carboxylic acid is acetic acid.

10. The process of claim 1 wherein the cobalt employed is obtained from cobaltous acetate tetrahydrate. 

2. The process of claim 1 wherein said alkyl phenyl sulfone contains an alkyl substituent on each ring.
 3. The process of claim 1 wherein said alkyl phenyl sulfone contains a methyl substituent on each ring.
 4. The process of claim 1 wherein said alkyl phenyl sulfone is p-tolyl sulfone.
 5. The process of claim 1 wherein said methylenic ketone is methyl ethyl ketone.
 6. The process of claim 1 wherein said methylenic ketone is cyclohexanone.
 7. The process of claim 1 wherein the reaction temperature is in the range of about 50* to about 200* C.
 8. The process of claim 1 wherein the reaction temperature is in the range of about 80* to about 125* C.
 9. The process of claim 1 wherein said lower carboxylic acid is acetic acid.
 10. The process of claim 1 wherein the cobalt employed is obtained from cobaltous acetate tetrahydrate. 